Heart failure is a condition in which a patient's heart works less efficiently than it should, resulting in the heart failing to supply the body sufficiently with the oxygen rich blood it requires, either at exercise or at rest. Congestive heart failure (CHF) is heart failure accompanied by a build-up of fluid pressure in the pulmonary blood vessels that perfuse the lungs. Transudation of fluid from the pulmonary veins into the pulmonary interstitial spaces, and eventually into the alveolar air spaces, is called pulmonary edema, and can cause shortness of breath, hypoxia, acidosis, respiratory arrest, and even death.
Chronic diseases such as CHF require close medical management to reduce morbidity and mortality. Because the disease status evolves with time, frequent physician follow-up examinations are typically necessary. At follow-up, the physician may make adjustments to the drug regimen in order to optimize therapy. This conventional approach of periodic follow-up is unsatisfactory for some diseases, such as CHF, in which acute, life-threatening exacerbations can develop between physician follow-up examinations. It is well know among clinicians that if a developing exacerbation is recognized early, it can be more easily and inexpensively terminated, typically with a modest increase in oral diuretic. However, if it develops beyond the initial phase, an acute heart failure exacerbation becomes difficult to control and terminate. Hospitalization in an intensive care unit is often required. It is during an acute exacerbation of heart failure that many patients succumb to the disease.
It is often difficult for patients to subjectively recognize a developing exacerbation, despite the presence of numerous physical signs that would allow a physician to readily detect it. Furthermore, since exacerbations typically develop over hours to days, even frequently scheduled routine follow-up with a physician cannot effectively detect most developing exacerbations. It is therefore desirable to have a system that allows for routine, frequent monitoring of patients so that an exacerbation can be recognized early in its course. With the patient and/or physician thus notified by the monitoring system of the need for medical intervention, a developing exacerbation can more easily and inexpensively be terminated early in its course.
Mitral valve regurgitation (MR) is a condition in which the mitral valve doesn't close tightly, which allows blood to flow backward in a patient's heart. When the mitral valve doesn't function properly, blood can't move through the heart or to the rest of the patient's body as efficiently. The condition can leave a patient fatigued and short of breath. As many as one in five people over age 55 have some degree of MR. Treatment of MR depends on the severity and progression of the condition and signs and symptoms. A patient may need heart surgery to repair or replace the valve. Left unchecked, severe MR can lead to CHF or serious heart rhythm irregularities (i.e., arrhythmias). MR is also called mitral insufficiency, mitral incompetence or simply mitral regurgitation.
Accordingly, it would be advantageous to provide implantable cardiac devices that can obtain information about a patient's heart failure progression and information about occurrences of MR. More generally, it is desirable to provide implantable cardiac devices that can obtain disease progression information.